Generally, plasma display panels are display devices in which ultraviolet (UV) light generated by gas discharge within discharge cells excites phosphors to display images. Plasma display panels are considered as next generation flat panel display devices because they can realize large-sized high-resolution display screens.
A plasma display panel configuration including a rear plate provided with an address electrode, a barrier rib, and a phosphor layer corresponding to each discharge cell, and a front plate provided with a discharge sustaining electrode having a scan electrode and a display electrode is introduced as an example of plasma display panel. The address electrode and the discharge sustaining electrode are covered with dielectric layers, and inside of the discharge cell is filled with a discharge gas. In such a PDP, an address discharge is generated when an address voltage is applied between the address electrode and the scan electrode. Due to the address discharge, wall charges are accumulated on the dielectric layers formed on the address electrode and the discharge sustaining electrode. In this way, a discharge cell in which a main discharge is to be triggered is selected. Then, when a sustain voltage is applied between the scan electrode and the display electrode of the selected discharge cell, positive ions accumulated on the scan electrode collide with electrons accumulated on the display electrode, thereby triggering the main discharge. The main discharge lowers an energy level of excited xenon (Xe) to emit UV light. The emission of UV light excites the phosphor coated inside the discharge cell. A visible light is emitted while an energy level of the excited phosphor is lowered. An image is reproduced by the emission of visible light.
When the plasma discharge occurs in the discharge cell, a magnesium oxide (MgO) layer on the dielectric layer of the front plate is directly exposed to plasma and thus is directly involved in the plasma discharge initiation and sustaining. In addition, the MgO layer is closely associated with electrical and optical characteristics of the PDP. A high secondary electron emission coefficient of the MgO layer decreases a discharge voltage of the discharge cell, thus reducing the total power consumption, and a high plasma ion durability plays an important role in extending the lifetime of the PDP. Furthermore, because the MgO layer has a high band gap energy of more than 7.8 eV, it can efficiently transmit the visible light generated when the UV light excites the phosphor.
Currently, the MgO layer of the PDP is formed on the dielectric layer of the front plate by E-beam evaporation, ion plating, etc. The MgO layer is directly associated with the plasma discharge and plays a crucial role in determining the total power consumption of the PDP. Hence, many researches and developments have been briskly conducted to reduce the plasma discharge firing voltage of the MgO layer. One of them is to adjust the crystallinity, density, and stress of the MgO layer through deposition and doping, and another is to form a new material for a passivation film which has better characteristics than the MgO layer. Meanwhile, the secondary electrons emitted from the MgO layer directly inducing the plasma discharge absorb and emit the energy generated when electrons inside the MgO layer tunnel into the MgO layer and are neutralized with positive ions of inert gas, e.g., neon (Ne). Therefore, the secondary electron emission is greatly dominated by surface characteristics rather than bulk characteristics such as the crystallinity, density, and stress of the MgO layer. However, studies based on this theory have not been sufficiently conducted. As one of efforts to substitute for the MgO layer, new materials for passivation films having good discharge characteristics have been reported, but their reliabilities are low compared with the MgO layer. Therefore, the new materials cannot be used in an actual manufacturing process.
Consequently, there is a limitation in researching and developing a passivation film having a low discharge firing voltage.